Switched mode power supplies are often used with mains driven applications having high and medium power rates in order to increase the efficiency of the application, and also to fulfil requirements regarding a necessity of nearly sinusoidal input currents to satisfy a standard, such as European standard EN 61000-3-2. Therefore, an active power factor correction (PFC) circuit is often used as a primary stage followed by a bulk capacitor that is used to smooth the output voltage and generate an output voltage that is as constant as possible (within economical justifiable limits) for subsequent DC-DC converters or loads.
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